Dual-mode silencer

Abstract

The present application provides a muffler assembly for a vehicle exhaust system, the muffler assembly comprising a muffler having: a main muffler duct with a main resonator; the auxiliary silencer pipeline is provided with an auxiliary resonator; and a valve that directs an exhaust flow through both the primary muffler duct and the secondary muffler duct, or mainly through the secondary muffler duct, depending on a position of the valve. The muffler provides a first level of sound attenuation when the valve is in the open position and a second level of sound attenuation when the valve is in the closed position. The muffler has a second level of sound attenuation greater than the first level of sound attenuation and thus provides a more loud exhaust sound when the valve is in the open position and a more quiet exhaust sound when the valve is in the closed position.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 534,472, filed on August 24, 2023. The entire disclosures of the above-referenced applications are incorporated herein by reference. Technical Field

[0003] The present application relates to vehicle exhaust systems, and more particularly to exhaust system mufflers and methods of making exhaust system mufflers. Background Art

[0004] The background technology provided here is for the purpose of generally presenting the context of the present application. The work of the presently named inventors (to the extent described in this section) and aspects of the description that may not otherwise qualify as prior art at the time of filing are neither explicitly nor implicitly admitted as prior art with respect to the present application.

[0005] Vehicles equipped with internal combustion engines typically direct the exhaust flow generated by the engine through a series of pipes commonly referred to as the vehicle exhaust system. The exhaust flow through the exhaust system typically increases with increasing engine speed, which changes the volume and note of the sound produced by the exhaust flow as it passes through the exhaust system. Many vehicle exhaust systems use active valves to change the sound level and / or sound characteristics (e.g., pitch) produced by the exhaust system during vehicle operation. Many vehicle manufacturers and exhaust system manufacturers refer to such systems as "Sport Exhaust" because they are a popular choice among racing enthusiasts who want louder or "sportier" exhaust sounds. Active valves (e.g., electromechanical valves) can be placed in the exhaust system to direct the exhaust flow to different pipes and / or chambers of the exhaust system to make the exhaust noise louder or quieter according to the driver's instructions. Typically, these active valves are controlled by pushing a button or other user interface inside the vehicle. Summary of the invention

[0006] This section provides a general summary of the application, and is not a comprehensive disclosure of its full scope or all of its features.

[0007] According to one aspect of the present application, a muffler assembly for a vehicle exhaust system is provided, the muffler assembly comprising a muffler having: a main muffler pipe with a main resonator; a secondary muffler pipe with a secondary resonator; and a valve, the valve directing the exhaust flow through both the main muffler pipe and the secondary muffler pipe or only through the secondary muffler pipe according to the position of the valve. The main resonator has a main resonator chamber, and the secondary resonator has a secondary resonator chamber. The main muffler pipe passes through the main resonator chamber to define a main exhaust flow path through the muffler. The secondary muffler pipe extends through at least a portion of the secondary resonator chamber to define a secondary exhaust flow path within the muffler.

[0008] The valve is positioned upstream of the main resonator and can be actuated between an open position and a closed position. Therefore, when the valve is in the open position, exhaust flow passing through both the main muffler pipe and the main exhaust flow path and through the secondary muffler pipe and the secondary exhaust flow path is allowed, which provides a first operating mode. Therefore, the muffler provides a first level of sound attenuation in the first operating mode. The valve restricts the exhaust flow passing through the main muffler pipe and the main exhaust flow path in the closed position, so that when the valve is in the closed position, more than 50% of the exhaust flow is directed through the secondary muffler pipe and the secondary exhaust flow path, which provides a second operating mode. The muffler therefore provides a second level of sound attenuation in the second operating mode. The second level of sound attenuation is greater than the first level of sound attenuation. Therefore, the muffler provides a louder exhaust sound (i.e., higher decibels) in the first operating mode and a quieter exhaust sound (i.e., lower decibels) in the second operating mode.

[0009] According to this aspect of the present application, the main resonator has a main resonator cross-sectional area (A1), and the main muffler pipe has a main muffler pipe cross-sectional area (a1) smaller than the main resonator cross-sectional area (A1). The sub-resonator has a sub-resonator cross-sectional area (A2), and the sub-muffler pipe has a sub-muffler pipe cross-sectional area (a2) smaller than the sub-resonator cross-sectional area (A2). The sizes of the main resonator and the sub-resonator and the main muffler pipe and the sub-muffler pipe are selected so that the main area ratio (A1 / a1) of the main resonator cross-sectional area (A1) divided by the main muffler pipe cross-sectional area (a1) is less than the secondary area ratio (A2 / a2) of the sub-resonator cross-sectional area (A2) divided by the sub-muffler pipe cross-sectional area (a2). This specific design specification enables the second (quieter) operating mode of the muffler to reduce the sound level generated by the vehicle exhaust system at any given engine speed (rpm) without a significant impact on the exhaust tone (i.e., frequency, pitch, resonance, burr, etc.). Thus, the acoustic characteristics of the exhaust note remain the same in the first operating mode and the second operating mode, the exhaust sound is simply quieter (ie, at a lower decibel level) in the second operating mode.

[0010] In some embodiments, the muffler assembly further comprises a primary inlet pipe arranged in fluid communication with the primary muffler conduit and a secondary inlet pipe arranged in fluid communication with the secondary muffler conduit and connected to the primary inlet pipe at a first junction outside the muffler.

[0011] In some embodiments, the primary resonator includes a primary resonator housing and the secondary resonator includes a secondary resonator housing separate and spaced apart from the primary resonator housing.

[0012] In some embodiments, the muffler assembly further comprises a main outlet pipe and a secondary outlet pipe, wherein the main outlet pipe is arranged in fluid communication with the main muffler pipe, and the secondary outlet pipe is arranged in fluid communication with the secondary muffler pipe and connected to the main outlet pipe at a second joint outside the muffler.

[0013] In some embodiments, the main muffler pipe has a perforated main pipe wall, which is tubular in shape and extends linearly from the main inlet pipe through the main resonator shell to the main outlet pipe, and wherein the secondary muffler pipe has a perforated secondary pipe wall, which is tubular in shape and extends linearly from the secondary inlet pipe through the secondary resonator shell to the secondary outlet pipe.

[0014] In some embodiments, the muffler assembly further comprises a main outlet pipe and a secondary outlet pipe, wherein the main outlet pipe is arranged to be in fluid communication with the main muffler pipe and comprises a main outlet pipe orifice, and the secondary outlet pipe is arranged to be in fluid communication with the secondary muffler pipe and comprises a secondary outlet pipe orifice spaced apart from the main outlet pipe orifice.

[0015] In the above embodiment, the muffler assembly further comprises a single outlet pipe arranged in fluid communication with the main muffler conduit.

[0016] In some embodiments, a main muffler pipe has a perforated main pipe wall, which is tubular in shape and extends linearly from a main inlet pipe through a main resonator shell to a single outlet pipe, wherein the main resonator is formed by a contraction tube, which is positioned inside the muffler shell and above the main pipe wall, so that a main resonator chamber is formed between the main pipe wall and the contraction tube, wherein a secondary muffler pipe has a perforated secondary pipe wall, which is tubular in shape and extends inside the muffler shell from the secondary inlet pipe to a second joint located inside the muffler shell, at which the secondary muffler pipe is joined to the main muffler pipe, and wherein a secondary resonator chamber is formed between the contraction tube and the muffler shell.

[0017] In some embodiments, the muffler includes a connector that fluidly connects the primary resonator chamber to the secondary resonator chamber.

[0018] In some embodiments, the valve is an active electromechanical valve including an electronic actuator connected to the movable valve member and driving movement of the movable valve member between the open position and the closed position.

[0019] In some embodiments, the primary and secondary muffler ducts are perforated pipes, and wherein at least one of the primary and secondary resonator chambers contains a sound dampening material.

[0020] In some embodiments, the main resonator cross-sectional area (A1) and the main muffler pipe cross-sectional area (a1) are substantially perpendicular to the exhaust flow passing through the main exhaust flow path, and wherein the sub-resonator cross-sectional area (A2) and the sub-muffler pipe cross-sectional area (a2) are substantially perpendicular to the exhaust flow passing through the sub-exhaust flow path. According to another aspect of the present application, a muffler assembly for a vehicle exhaust system is provided, the muffler assembly including a muffler having: a main muffler pipe with a main resonator; a sub-muffler pipe with a sub-resonator; and a valve, the valve directing the exhaust flow through both the main muffler pipe and the sub-muffler pipe or mainly through the sub-muffler pipe according to the position of the valve. The main muffler pipe, the main resonator, the sub-muffler pipe and the sub-resonator are positioned inside the muffler housing. More specifically, the main muffler pipe passes through the main resonator and the muffler housing to define the main exhaust flow path passing through the muffler. The sub-muffler pipe extends within the muffler housing to define the sub-exhaust flow path within the muffler.

[0021] Likewise, the valve is positioned upstream of the main resonator and is actuable between an open position and a closed position. Thus, when the valve is in the open position, exhaust flow passing through both the main muffler pipe and the main exhaust flow path and through the secondary muffler pipe and the secondary exhaust flow path is allowed, which provides a first operating mode. Thus, the muffler provides a first level of sound attenuation in the first operating mode. The valve limits the exhaust flow passing through the main muffler pipe and the main exhaust flow path in the closed position, so that when the valve is in the closed position, more than 50% of the exhaust flow is directed through the secondary muffler pipe and the secondary exhaust flow path, which provides a second operating mode. The muffler therefore provides a second level of sound attenuation in the second operating mode. The second level of sound attenuation is greater than the first level of sound attenuation. Thus, the muffler provides a louder exhaust sound (i.e., higher decibels) in the first operating mode and a quieter exhaust sound (i.e., lower decibels) in the second operating mode.

[0022] According to this aspect of the application, the main resonator is formed by a first pinch can, which is positioned inside the muffler shell and above the main muffler pipe, so that a main resonator chamber is formed between the main muffler pipe and the first pinch can. The secondary resonator includes a secondary resonator chamber formed between the first pinch can and the muffler shell. The secondary muffler pipe is connected to the first muffler pipe fluidically at a second pinch can positioned inside the muffler shell. The second pinch can is adjacent to the first pinch can and is positioned above the main muffler pipe, so that a diffusion chamber is formed between the main muffler pipe and the second pinch can. The main muffler pipe includes circumferentially spaced openings that allow the exhaust flow to pass through the secondary muffler pipe and the diffusion chamber in the second pinch can, thereby entering the main muffler pipe with reduced turbulence and flow noise.

[0023] In some embodiments, the muffler housing includes an outer shell closed at opposite ends by an inlet header and an outlet header, wherein the inlet header includes a primary inlet aperture and a secondary inlet aperture, and wherein the outlet header includes a single outlet aperture.

[0024] In some embodiments, the main muffler duct has a perforated main duct wall that is tubular in shape and extends linearly through the muffler housing from a main inlet aperture in the inlet header to a single outlet aperture in the outlet header.

[0025] In some embodiments, the second converging barrel includes a converging barrel inlet, and wherein the secondary muffler pipe has a perforated secondary pipe wall, which is tubular in shape and extends within the muffler shell from the secondary inlet orifice in the inlet header to the converging barrel inlet of the second converging barrel.

[0026] In some embodiments, the circumferentially spaced openings in the main muffler pipe are positioned along a limited arc length, thereby leaving an unperforated area in the main pipe wall aligned with the convergent barrel inlet of the second convergent barrel, so that the exhaust flow in the diffusion chamber of the second convergent barrel is dispersed outward around the circumference of the main pipe wall and further reduces turbulence and flow noise.

[0027] In some embodiments, the muffler housing includes an outer shell including a primary inlet aperture, a secondary inlet aperture, a primary outlet aperture, and a secondary outlet aperture.

[0028] In some embodiments, the muffler assembly includes a connector that connects the main resonator chamber to the fluid of the secondary resonator chamber. According to another aspect of the present application, a method for assembling the above-mentioned muffler assembly is provided. The method includes the following steps: assembling the main resonator by positioning the first contraction tube above the main muffler pipe; connecting the main muffler pipe to the main inlet orifice in the inlet header of the muffler shell; and connecting the secondary muffler pipe to the secondary inlet orifice in the inlet header of the muffler shell. The method also includes the following steps: installing the main muffler pipe and the secondary muffler pipe inside the shell of the muffler shell to form a secondary resonator inside the muffler shell; and connecting the main muffler pipe to the single outlet orifice in the outlet header of the muffler shell.

[0029] The method further includes the steps of positioning a second converging barrel above the main muffler pipe to form a diffusion chamber between the main muffler pipe and the second converging barrel, positioning the second converging barrel to be arranged adjacent to the first converging barrel, and securing the second converging barrel to the first converging barrel. According to these steps, the diffusion chamber is arranged to be in fluid communication with the main muffler pipe through circumferentially spaced openings in the main muffler pipe. The method further includes the steps of connecting the secondary muffler pipe in fluid communication with the converging barrel inlet on the second converging barrel to form a joint between the main muffler pipe and the secondary muffler pipe inside the muffler housing.

[0030] In some embodiments, the step of positioning the second shrink tube to be arranged adjacent to the first shrink tube and fixing the second shrink tube to the first shrink tube is performed after the step of positioning the second shrink tube above the main muffler pipe, and the method provided in the present application also includes sliding a portion of the second shrink tube over the first shrink tube in a sliding fit manner before fixing the second shrink tube to the first shrink tube.

[0031] In some embodiments, the step of positioning the second shrink tube to be arranged adjacent to the first shrink tube and fixing the second shrink tube to the first shrink tube is performed before the step of positioning the second shrink tube above the main muffler pipe, and the method provided by the present application also includes sliding a portion of the second shrink tube over the first shrink tube in a sliding fit manner before fixing the second shrink tube to the first shrink tube. Other areas of applicability of the present application will become apparent from the detailed description, claims and drawings. The detailed description and specific examples are intended for illustrative purposes only and are not intended to limit the scope of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present application will be more fully understood through the detailed description and accompanying drawings, in which:

[0033] Figure 1is a top plan view of an exemplary vehicle exhaust system equipped with a muffler assembly constructed in accordance with the present application;

[0034] Figure 2 yes Figure 1 a top cross-sectional view of one of the exemplary muffler assemblies illustrated in FIG.

[0035] Figure 3 yes Figure 2 a partial top cross-sectional view of an exemplary muffler assembly illustrated;

[0036] Figure 4 yes Figure 2 Another top cross-sectional view of the exemplary muffler assembly illustrated in , showing several weld joints in the muffler assembly;

[0037] Figure 4A is a top cross-sectional view of an alternative muffler assembly including a connector;

[0038] Figure 4B is a top cross-sectional view of another alternative muffler assembly;

[0039] Figure 5 This is an example assembly Figure 2 A flow chart of an exemplary method of an exemplary muffler assembly as illustrated in;

[0040] Figure 6 This is an example assembly Figure 2 Another flow chart of another exemplary method of the exemplary muffler assembly illustrated in;

[0041] Figure 7 is a top cross-sectional view of another exemplary muffler assembly, wherein the active valve is shown in an open position such that exhaust flow through the muffler assembly passes through a primary muffler conduit and a secondary muffler conduit and provides a first operating mode having a louder exhaust sound;

[0042] Fig. 7A is a top cross-sectional view of another exemplary muffler assembly including a connector;

[0043] Figure 7B is a top cross-sectional view of another alternative muffler assembly; and

[0044] Figure 8 yes Figure 7 A top cross-sectional view of an exemplary muffler assembly illustrated in FIG. 1 , wherein the active valve is shown in a closed position such that exhaust flow through the muffler assembly passes through the secondary muffler conduit and provides a second operating mode with a quieter exhaust sound.

[0045] Among the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0046] Referring to the drawings, wherein like numerals indicate corresponding parts throughout the several views, a muffler assembly 100 , 200 for a vehicle exhaust system 10 is disclosed.

[0047] Example embodiments are provided so that the present application will be thorough and the scope will be fully conveyed to those skilled in the art. Many specific details, such as examples of specific components, devices, and methods, are set forth to provide a thorough understanding of the embodiments of the present application. It will be apparent to those skilled in the art that specific details need not be employed, that the example embodiments may be embodied in many different forms, and should not be construed as limiting the scope of the present application. In some example embodiments, well-known processes, well-known device structures, and well-known techniques are not described in detail.

[0048] The terms used herein are only used for the purpose of describing specific example embodiments and are not intended to be limiting. As used herein, unless the context clearly states otherwise, the singular forms "one", "a kind of" and "the" may also be intended to include plural forms. The terms "including" and "having" are inclusive, and therefore specify the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or their groups. Unless there is a clear order of execution, the method steps, processes and operations described herein should not be interpreted as having to be performed in the specific order discussed or illustrated. It should also be understood that additional or alternative steps may be adopted.

[0049] When an element or layer is referred to as being "located on," "engaged to," "connected to," or "coupled to" another element or layer, the element or layer may be directly located on, engaged to, connected to, or coupled to another element or layer, or there may be intermediate elements or layers. Conversely, when an element is referred to as being "directly located on," "directly engaged to," "directly connected to," or "directly coupled to" another element or layer, there may be no intermediate elements or layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "located between" versus "directly located between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0050] Although the term first, second, third etc. can be used to describe various elements, components, regions, layers and / or sections in this article, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms may only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly states, otherwise the terms used herein such as "first", "second" and other numerical terms do not mean sequence or order. Therefore, without departing from the teaching content of the example embodiment, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section.

[0051] Spatially relative terms such as "inside", "outside", "below", "below", "lower", "above", "upper", etc. may be used herein to facilitate description of the relationship of one element or feature to another (additional) element or feature, as illustrated in the figure. In addition to the orientations depicted in the figures, spatially relative terms may also be intended to cover different orientations of the device in use or operation. For example, if the device in the accompanying drawings is turned over, then the elements described as "below" or "below" other elements or features will be oriented to be "above" other elements or features. Therefore, the example term "below" can cover the orientations of above and below. The device can be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein are interpreted accordingly.

[0052] refer to Figure 1 , an exemplary vehicle exhaust system 10 is illustrated. The illustrated vehicle exhaust system 10 is an automobile exhaust system designed to transport exhaust gas generated by an internal combustion engine from one or more exhaust inlets 12 located at the front of the vehicle exhaust system 10 to one or more exhaust outlets 14 located at the rear of the vehicle exhaust system 10. Figure 1 In FIG. 1 , the vehicle exhaust system 10 includes a first exhaust run 16 positioned closer to the right side of the vehicle and a second exhaust run 18 positioned closer to the left side of the vehicle. Figure 1 In the exhaust system, each exhaust path 16 , 18 has an inlet 12 and an outlet 14 , one or more exhaust pipe segments 20 and a resonator 22 . Figure 1 The vehicle exhaust system 10 shown in FIG. 1 also includes a mixing section 24 such as an X-pipe that connects the first exhaust stroke 16 and the second exhaust stroke 18 to each other in fluid communication. It should be understood that the inlet 12 is configured to be connected to the outlet of a catalytic converter, an exhaust header, an exhaust header downpipe, or other exhaust system components, and thus receives exhaust gas and heat generated by the internal combustion engine. The outlet 14 leads to the atmosphere, and thus releases the exhaust gas and heat to the environment. Figure 1Each of the exhaust strokes 16, 18 shown has one resonator 22 located upstream of the mixing section 24 (i.e., between the inlet 12 and the mixing section 24) and a muffler assembly 100 located downstream of the mixing section 24 (i.e., between the mixing section 24 and the outlet 14). The muffler assembly 100 is specifically designed to provide a first operating mode with a louder exhaust sound and a second operating mode with a quieter exhaust sound for any given engine speed (rpm) without changing the acoustic characteristics of the exhaust sound (i.e., frequency, pitch, resonance, burrs, etc.) other than the sound level (dB).

[0053] Figure 1 The vehicle exhaust system 10 shown in is specifically designed for use in an automobile equipped with an inline six-cylinder engine having twin turbochargers, wherein one turbocharger receives exhaust gas from three of the six cylinders and the other turbocharger receives exhaust gas from the other three cylinders. Thus, the exhaust manifold from one of the turbochargers delivers exhaust gas from three of the cylinders to the inlet 12 of the first exhaust stroke 16, and the exhaust manifold from the other turbocharger delivers exhaust gas from the other three cylinders to the inlet 12 of the second exhaust stroke 18. A specific problem faced by the inventors in the development of the muffler assemblies 100, 200 described below is how to produce such a muffler assembly that simultaneously provides these two different operating modes without changing the characteristics of the exhaust note when switching between the loud operating mode and the quiet operating mode. A secondary problem faced by the inventors is how to make such a muffler assembly that supplies a single outlet 14 per exhaust stroke 16, 18.

[0054] Although the muffler assemblies 100, 200 described herein are developed using Figure 1 The particular exhaust system arrangement depicted and the related issues described above are intended to be followed, but it should be understood that Figure 1 Only one exemplary configuration of vehicle exhaust system 10 is illustrated, and many other exhaust system configurations are possible, including but not limited to having no exhaust system 10. Figure 1 Exhaust system configurations of the illustrated resonator 22 and / or mixing section 24, exhaust systems having multiple outlets 14 per exhaust path 16, 18, and exhaust systems having only one exhaust path instead of Figure 1 The illustrated exhaust system has two exhaust paths 16, 18. Therefore, the muffler assembly 100, 200 shown and described herein can be utilized in various vehicle exhaust systems and is not limited to application in Figure 1 An exemplary vehicle exhaust system 10 is shown.

[0055] Still reference Figure 1, each muffler assembly 100 includes a muffler 101. The muffler 101 includes a muffler housing 102 having an outer shell 104, the outer shell having a generally elliptical cross-sectional shape and being closed at the inlet end and the outlet end by an inlet header 106 and an outlet header 108. Each muffler assembly 100 also includes a main inlet pipe 103 and a secondary inlet pipe 105 connected to the inlet header 106 of the muffler 101 and a single outlet pipe 107 connected to the outlet header 108. The main inlet pipe 103 and the secondary inlet pipe 105 are connected at a joint 109, which connects the main inlet pipe 103 and the secondary inlet pipe 105 to the exhaust pipe segment 20 in each of the first exhaust stroke 16 and the second exhaust stroke 18. The main inlet pipe 103 has a larger diameter than the secondary inlet pipe 105. The active electromechanical valve 111 is positioned in the primary inlet pipe 103 and is actuable between an open position, in which exhaust gas flow through the primary inlet pipe 103 is permitted, and a closed position, in which the active electromechanical valve 111 blocks and thereby restricts exhaust gas flow through the primary inlet pipe 103. As will be explained in more detail below, the open position of the active electromechanical valve 111 provides a first operating mode in which exhaust gas flows into the muffler assembly 100 through both the primary inlet pipe 103 and the secondary inlet pipe 105, and in which the sound attenuation provided by the muffler assembly 100 is minimal to produce a loud exhaust sound. The closed position of the active electromechanical valve 111 provides a second operating mode in which all or a majority (i.e., more than 50%) of the exhaust gas flow entering the muffler assembly 100 passes through the secondary inlet pipe 105, which results in greater sound attenuation by the muffler assembly 100 as compared to the first operating mode and a quieter exhaust sound that still maintains the same exhaust note but at a lower decibel level (dB).

[0056] Additional references Figure 2, the muffler 101 includes a main muffler pipe 113 and a secondary muffler pipe 115. The main muffler pipe 113 extends linearly from the inlet header 106 across the muffler housing 102 to the outlet header 108 (i.e., the main muffler pipe 113 is a straight pipe or pipe). The main muffler pipe 113 has a main pipe wall 117, which is tubular in shape and includes a first set of perforations 118. The main pipe wall 117 extends linearly between an upstream main pipe end 119 and a downstream main pipe end 121. The inlet header 106 includes a main inlet orifice 123 that receives the upstream main pipe end 119 with a close tolerance fit, and the outlet header 108 includes a single outlet orifice 125 that receives the downstream main pipe end 121 with a close tolerance fit. The downstream end of the main inlet pipe 103 is received in the main inlet orifice 123 and the upstream main pipe end 119 with a close tolerance fit to form an overlapping joint. The upstream end of the single outlet pipe 107 is received in the single outlet aperture 125 and the downstream main pipe end 121 with a close tolerance fit to form an overlapping joint. Thus, the main muffler pipe 113 is arranged to be in fluid communication with the main inlet pipe 103 and the single outlet pipe 107 and to carry exhaust gas therebetween, and thus define a main exhaust gas flow path 127 through the muffler 101.

[0057] The secondary muffler pipe 115 has a secondary pipe wall 129 that is tubular in shape and includes a second set of perforations 131. The secondary pipe wall 129 is curved and extends between an upstream secondary pipe end 133 and a downstream secondary pipe end 135. The inlet header 106 includes a secondary inlet aperture 137 that receives the upstream secondary pipe end 133 with a close tolerance fit. The downstream end of the secondary inlet pipe 105 is received in the secondary inlet aperture 137 and the upstream secondary pipe end 133 with a close tolerance fit to form an overlapping joint. Therefore, the secondary muffler pipe 115 defines a secondary exhaust flow path 138 through the muffler 101.

[0058] The muffler 101 also includes a main resonator 139 and a sub-resonator 141 positioned inside the muffler shell 102. The main resonator 139 is formed by a first contraction tube 143 positioned inside the muffler shell 102. More specifically, the first contraction tube 143 is positioned above the main muffler pipe 113. The first contraction tube 143 has a first contraction tube wall 145, which is tubular in shape and extends linearly between an upstream first contraction tube end 147 and a downstream first contraction tube end 149. Therefore, a main resonator chamber 151 is formed by the space between the main pipe wall 117 and the first contraction tube wall 145. The sub-resonator 141 includes a sub-resonator chamber 153, which is formed by the space between the first contraction tube 143 and the muffler shell 102. The first set of perforations 118 in the main pipe wall 117 is arranged to be in fluid communication with the main resonator chamber 151 and is designed to propagate sound from the main muffler pipe 113 to the main resonator chamber 151. The second set of perforations 131 in the secondary pipe wall 129 is arranged to be in fluid communication with the secondary resonator chamber 153 and is designed to propagate sound from the secondary muffler pipe 115 to the secondary resonator chamber 153. The main resonator chamber 151 and / or the secondary resonator chamber 153 may, but need not, contain a sound damping material 155. As an example and not limitation, the sound damping material 155 may be a glass fiber roving, which is designed to absorb and attenuate sound within a specific frequency range. Therefore, it should be understood that the main resonator chamber 151 and the secondary resonator chamber 153 in the muffler 101 only serve to attenuate sound, and they themselves do not define any exhaust flow path within the muffler 101. In other words, the main resonator chamber 151 and the sub-resonator chamber 153 act as trapped volumes within the muffler 101 and are not designed with inlets and outlets for exhaust gas flow. Optionally, one or more baffles 157 may be positioned within the sub-resonator chamber 153 to tune the resonant frequency range within the sub-resonator chamber 153.

[0059] The main resonator 139 has a main resonator cross-sectional area A1 defined by the first contraction tube 143, and the main muffler pipe 113 has a main muffler pipe cross-sectional area a1 that is smaller than the main resonator cross-sectional area A1. The sub-resonator 141 has a sub-resonator cross-sectional area A2 defined by the outer shell 104 of the muffler shell 102, and the sub-muffler pipe 115 has a sub-muffler pipe cross-sectional area a2 that is smaller than the sub-resonator cross-sectional area A2. It should be understood that the main resonator cross-sectional area A1 and the main muffler pipe cross-sectional area a1 are substantially perpendicular to the exhaust flow passing through / along the main exhaust flow path 127, and the sub-resonator cross-sectional area A2 and the sub-muffler pipe cross-sectional area a2 are substantially perpendicular to the exhaust flow passing through / along the sub-exhaust flow path 138. The main resonator 139 and the sub-resonator 141 as well as the main muffler pipe 113 and the sub-muffler pipe 115 are sized so that the main area ratio A1 / a1 of the main resonator cross-sectional area A1 divided by the main muffler pipe cross-sectional area a1 is less than the sub-area ratio A2 / a2 of the sub-resonator cross-sectional area A2 divided by the sub-muffler pipe cross-sectional area a2. For example, the main resonator 139 (as defined by the first constriction tube 143) and the main muffler pipe 113 are sized so that the main area ratio A1 / a1 of the main resonator cross-sectional area A1 divided by the main muffler pipe cross-sectional area a1 may be greater than 1 and less than 4. The sub-resonator 141 (as defined by the shell 104 of the muffler housing 102) and the sub-muffler pipe 115 are sized so that the sub-area ratio A2 / a2 of the sub-resonator cross-sectional area A2 divided by the sub-muffler pipe cross-sectional area a2 may be greater than 4 and less than 100. This particular geometry enables the second (quieter) operating mode of the muffler 101 to reduce the sound level produced by the vehicle exhaust system 10 at any given engine speed (rpm) without significantly affecting the exhaust note (i.e., frequency, pitch, resonance, burrs, etc.). Thus, the acoustic characteristics of the exhaust note remain the same in the first operating mode and the second operating mode, the exhaust sound is simply quieter (i.e., at a lower decibel level) in the second operating mode.

[0060] Additional references Figure 3 , the secondary muffler duct 115 is connected to the main muffler duct 113 in fluid communication via a second converging barrel 159 positioned inside the muffler housing 102. The second converging barrel 159 includes a second converging barrel wall 161 extending between an upstream second converging barrel end 163 and a downstream second converging barrel end 165. The second converging barrel 159 is positioned above the main muffler duct 113, and the upstream second converging barrel end 163 abuts the downstream first converging barrel end 149 in an overlapping close tolerance sliding fit, so that a diffusion chamber 167 is formed between the main duct wall 117 and the second converging barrel wall 161. The second converging barrel wall 161 includes a converging barrel inlet 169, which receives the downstream secondary duct end 135 in a close tolerance fit to form an overlapping joint.

[0061] The main muffler duct 113 includes circumferentially spaced openings 171 in the main duct wall 117 that allow the exhaust flow to pass through the secondary muffler duct 115 and the diffusion chamber 167 in the second convergent barrel 159, thereby entering the main muffler duct 113 with reduced turbulence and flow noise. The circumferentially spaced openings 171 in the main duct wall 117 are positioned along a limited arc length, leaving an unperforated area 173 in the main duct wall 117 that is aligned with the convergent barrel inlet 169 of the second convergent barrel 159. When the exhaust flow leaves the downstream secondary duct end 135 and enters the diffusion chamber 167 in the second convergent barrel 159, the unperforated area 173 of the main duct wall 117 prevents the exhaust flow from immediately entering the main muffler duct 113 and forces the exhaust flow in the diffusion chamber 167 to disperse outwardly around the circumference of the main duct wall 117 before entering the main muffler duct 113. Thus, as exhaust gases enter the main muffler duct 113, exhaust gases in the diffusion chamber 167 of the second converging barrel 159 flow radially inwardly through the circumferentially spaced openings 171 in the main duct wall 117. This arrangement further reduces turbulence and flow noise.

[0062] like Figure 4A As depicted, an alternative muffler 101a is depicted. Muffler 101a is substantially similar to muffler 101. Therefore, similar elements will be identified with similar reference numerals including the suffix "a". The main and perhaps only difference between muffler 101a and muffler 101 relates to connector 110a, which serves as a conduit interconnecting the main resonator chamber 151a with the secondary resonator chamber 153a. It is contemplated that muffler 101a may include a plurality of connectors 110a extending through the converging barrel wall 145a at spaced-apart locations. Alternatively, connector 110a may be simply defined as an orifice extending through the first converging barrel 143a without the presence of an additional cylindrical pipe.

[0063] Figure 4B Another alternative muffler 101b is depicted in FIG. Muffler 101b is substantially similar to muffler 101. Therefore, similar elements will be identified with similar reference numerals including the suffix "b". The main difference between muffler 101b and muffler 101 is the provision of secondary outlet orifice 126b at secondary duct end 135b of secondary muffler duct 115b. It should be understood that secondary duct wall 129b no longer turns toward second converging barrel 159a. Secondary muffler duct 115b does not meet converging barrel inlet 169 ( Figure 4 ) meet or fluidly communicate. In contrast, the auxiliary muffler pipe 115b can be formed as a right circular hollow cylinder extending along a straight line, such as Figure 4B Depicted.

[0064] What was previously referred to as the single outlet aperture 125 associated with the muffler 101 is now identified as the primary outlet aperture 125b. In this arrangement, the exhaust flow path 127b is not connected to the exhaust flow path 138b downstream of the decay volume.

[0065] Back to Figures 1 to 4 The first shrink tube 143 and the second shrink tube 159 can be fixed to the main muffler pipe 113 in a variety of different ways. For example, but not limited to, the first shrink tube 143 and the second shrink tube 159 can be fixed to the main muffler pipe 113 in a variety of different ways. Figure 4 The first converging sleeve end 147 is welded to the main muffler pipe 113 at the weld joints 175a to 175d shown. According to this example, the upstream first converging sleeve end 147 can be welded to the main pipe wall 117 at the weld joint 175a. Similarly, the downstream first converging sleeve end 149 can be welded to the main pipe wall 117 at the weld joint 175b. The upstream second converging sleeve end 163 is configured to slide over the downstream first converging sleeve end 149 in an overlapping close tolerance sliding fit and is fixed to the first converging sleeve wall 145 by the weld joint 175c. The upstream second converging sleeve end 163 can be spot welded to the downstream first converging sleeve end 149 to form one or more local weld joints 175c spaced circumferentially around the first converging sleeve wall 145, because the overlapping fit between the upstream second converging sleeve end 163 and the downstream first converging sleeve end 149 provides a seal (i.e., the weld joint 175c does not have to provide a seal). Finally, the downstream second converging sleeve end 165 can be welded to the main pipe wall 117 at the weld joint 175d. Although many different welding operations can be utilized, by way of example and not limitation, weld joints 175a, 175b, and 175c can be produced by stitch welding, spot welding, or a rotation operation. Alternatively, weld joints 175a, 175b, and 175c can be replaced by spine lock connections.

[0066] refer to Figure 5 , illustrates a method of assembling the above-described muffler 101. The method includes step 1A of assembling the main resonator 139 by positioning the first converging tube 143 over the main muffler duct 113 and step 2A of securing the upstream first converging tube end 147 and the downstream first converging tube end 149 to the main duct wall 117 by forming weld joints 175a and 175b. The method then proceeds to step 3A of positioning / sliding the second converging tube 159 over the main muffler duct 113 until the upstream second converging tube end 163 receives the downstream first converging tube end 149 in a sliding fit and abutting arrangement to form a diffusion chamber 167 between the main muffler duct 113 and the second converging tube 159, which is arranged to be in fluid communication with the main muffler duct 113 through circumferentially spaced openings 171 in the main duct wall 117.

[0067] Therefore, according to Figure 5 The method shown, after step 1A of assembling the main resonator 139 by positioning the first tapered tube 143 above the main muffler pipe 113 and step 2A of fixing the upstream first tapered tube end 147 and the downstream first tapered tube end 149 to the main pipe wall 117, step 3A of positioning the second tapered tube 159 above the main muffler pipe 113 until the upstream second tapered tube end 163 abuts the downstream first tapered tube end 149 is performed. Figure 5 The illustrated method continues with step 4A by securing the upstream second converging sleeve end 163 to the first converging sleeve wall 145 by forming a weld joint 175c and securing the downstream second converging sleeve end 165 to the main conduit wall 117 by forming a weld joint 175d.

[0068] Figure 5 The method shown in also includes step 5A, that is, connecting the downstream secondary pipe end 135 to the converging tube inlet 169 on the second converging tube 159 to form a joint between the main muffler pipe 113 and the secondary muffler pipe 115 inside the muffler shell 102. The method also includes step 6A of connecting the upstream main pipe end 119 to the main inlet orifice 123 in the inlet header 106, step 7A of connecting the upstream secondary pipe end 133 to the secondary inlet orifice 137 in the inlet header 106, step 8A of installing the main muffler pipe 113 and the secondary muffler pipe 115 and the first converging tube 143 and the second converging tube 159 inside the shell 104 of the muffler shell 102 (which forms the secondary resonator 141 inside the muffler shell 102), and step 9A of connecting the downstream main pipe end 121 to the single outlet orifice 125 in the outlet header 108. It should be understood that steps 5A to 9A can be performed in the same manner as described above and Figure 5 The steps may be performed in an order different from the order illustrated in FIG. 1 , and one or more of steps 5A to 9A may be performed before one or more of steps 1A to 4A.

[0069] refer to Figure 6, illustrates an alternative method of assembling the above-described muffler 101. The alternative method includes step 1B of positioning / sliding the downstream first converging barrel end 149 into the upstream second converging barrel end 163 in a sliding fit to form an abutting arrangement between the first converging barrel 143 and the second converging barrel 159, and step 2B of securing the downstream first converging barrel end 149 to the upstream second converging barrel end 163 by forming a weld 175c. The method continues with step 3B of positioning / sliding the first converging barrel 143 and the second converging barrel 159 over the main muffler duct 113 to form a main resonator 139 and a diffusion chamber 167 between the main muffler duct 113 and the second converging barrel 159, the diffusion chamber being arranged to be in fluid communication with the main muffler duct 113 through circumferentially spaced openings 171 in the main duct wall 117.

[0070] Therefore, according to Figure 6 The method shown, before step 3B of positioning / sliding the first contraction tube 143 and the second contraction tube 159 over the main muffler pipe 113 to form the main resonator 139 and the diffusion chamber 167, performs step 1B of positioning / sliding the downstream first contraction tube end 149 into the upstream second contraction tube end 163 in a sliding fit manner to form an adjacent arrangement between the first contraction tube 143 and the second contraction tube 159 and step 2B of fixing the downstream first contraction tube end 149 to the upstream second contraction tube end 163. Figure 6 The method shown in then proceeds to step 4B, which is to secure the upstream first and downstream first and downstream second converging sleeve ends 147, 149, and 165 to the main pipe wall 117 by forming weld joints 175a, 175b, and 175d.

[0071] Figure 6 The method shown in also includes step 5B, which is to connect the downstream secondary pipe end 135 to the converging tube inlet 169 on the second converging tube 159 to form a joint between the main muffler pipe 113 and the secondary muffler pipe 115 inside the muffler shell 102. The method also includes step 6B of connecting the upstream main pipe end 119 to the main inlet orifice 123 in the inlet header 106, step 7B of connecting the upstream secondary pipe end 133 to the secondary inlet orifice 137 in the inlet header 106, step 8B of installing the main muffler pipe 113 and the secondary muffler pipe 115 and the first converging tube 143 and the second converging tube 159 inside the shell 104 of the muffler shell 102 (which forms the secondary resonator 141 inside the muffler shell 102), and step 9B of connecting the downstream main pipe end 121 to the single outlet orifice 125 in the outlet header 108. It should be understood that steps 5B to 9B can be performed in the same manner as described above and Figure 6The steps may be performed in an order different from the order illustrated in the flowchart, and one or more of steps 5B to 9B may be performed before one or more of steps 1B to 4B.

[0072] refer to Figure 7 and Figure 8 , exemplifies the Figure 1 Another muffler assembly 200 of the vehicle exhaust system 10 is shown. Figure 7 and Figure 8 The muffler assembly 200 shown in FIG. Figures 1 to 4 The muffler assembly 100 illustrated in FIG. 1 shares many of the same components, but in Figure 7 and Figure 8 In the embodiment of the present invention, the main resonator 239 and the sub-resonator 241 of the muffler 201 are separate components separated by a small gap. The following paragraphs describe Figure 7 and Figure 8 New and / or different from the combination Figures 1 to 4 Rather than repeating the above description, the structure and function of the components of those shown and described will be described. It should be understood that Figures 1 to 4 The reference numbers in the examples are "100" serial numbers (e.g., 100, 102, 104, etc.), while Figure 7 and Figure 8 Zhongyu Figures 1 to 4 Components identical or similar to the components of the muffler assembly 100 shown in FIG. 1 share the same basic reference numbers, but are listed as "200" serial numbers (e.g., 200, 202, 204, etc.). Thus, the same description of the element 100 above applies to the Figure 7 and Figure 8 Component 200, and so on.

[0073] The muffler assembly 200 includes a muffler 201 including a main resonator 239 having a main resonator chamber 251 and a sub-resonator 241 having a sub-resonator chamber 253. The main muffler pipe 213 passes through the main resonator chamber 251 to define a main exhaust flow path 227 through the muffler 201. The sub-muffler pipe 215 passes through the sub-resonator chamber 253 to define a sub-exhaust flow path 238 through the muffler 201. The main resonator 239 includes a main resonator housing 202a, and the sub-resonator 241 includes a sub-resonator housing 202b separated and spaced apart from the main resonator housing 202a. Each of the main and sub-resonator housings 202a, 202b has a housing 204a, 204b having a substantially circular cross-sectional shape and closed at the inlet and outlet ports by a main or sub-inlet header 206a, 206b and a main or sub-outlet header 208a, 208b, respectively.

[0074] The muffler assembly 200 also includes a main inlet pipe 203 connected to the main inlet manifold 206a, a secondary inlet pipe 205 connected to the secondary inlet manifold 206b, a main outlet pipe 207a connected to the main outlet manifold 206a, and a secondary outlet pipe 207b connected to the secondary outlet manifold 208b. The main inlet pipe 203 has a larger diameter than the secondary inlet pipe 205, and the main outlet pipe 207a has a larger diameter than the secondary outlet pipe 207b. The main inlet pipe 203 and the secondary inlet pipe 205 are connected at the first joint 209a outside the muffler 201 and upstream, and the first joint makes the main inlet pipe 203 and the secondary inlet pipe 205 fluidly connected to each other. The main outlet pipe 207a and the secondary outlet pipe 207b are connected at the second joint 209b outside the muffler 201 and downstream, and the second joint makes the main outlet pipe 207a and the secondary outlet pipe 207b fluidly connected to each other.

[0075] The active electromechanical valve 211 is positioned in the main inlet pipe 203 and can be in an open position (eg Figure 7 as shown) and the closed position (as Figure 8 203 ), in the open position, allowing exhaust gas flow through the main inlet pipe 203, and in the closed position, the active electromechanical valve 211 blocks and thus restricts exhaust gas flow through the main inlet pipe 203. Figure 7 As shown in , the open position of the active electromechanical valve 211 provides a first operating mode in which exhaust gas flows into the muffler 201 through both the primary inlet pipe 203 and the secondary inlet pipe 205, and in which the sound attenuation provided by the muffler 201 is minimal to produce a loud exhaust sound. Figure 8 As shown, the closed position of the active electromechanical valve 211 provides a second operating mode in which all or a majority (i.e., more than 50%) of the exhaust flow entering the muffler 201 passes through the secondary inlet pipe 205, which results in greater sound attenuation by the muffler 201 as compared to the first operating mode and a quieter exhaust sound that still maintains the same exhaust tone but at a lower decibel level (dB).

[0076] Still reference Figure 7 and Figure 8, the main muffler pipe 213 extends linearly from the main inlet header 206a across the main resonator shell 202a to the main outlet header 208a (i.e., the main muffler pipe 213 is a straight pipe or tube). The main muffler pipe 213 has a main pipe wall 217 that is tubular in shape and includes a first set of perforations 218. The main pipe wall 217 extends linearly between an upstream main pipe end 219 and a downstream main pipe end 221. The main inlet header 206a includes a main inlet orifice 223 that receives the upstream main pipe end 219 with a close tolerance fit, and the main outlet header 208a includes a main outlet orifice 225a that receives the downstream main pipe end 221 with a close tolerance fit. The downstream end of the main inlet pipe 203 is received in the main inlet orifice 223 and the upstream main pipe end 219 with a close tolerance fit to form an overlapping joint. The upstream end of the main outlet pipe 207a is received in the main outlet aperture 225a and the downstream main pipe end 221 with a close tolerance fit to form an overlapping joint. Thus, the main muffler pipe 213 is arranged to be in fluid communication with the main inlet pipe 203 and the main outlet pipe 207a and to carry exhaust gas therebetween to define a main exhaust gas flow path 227 through the muffler 201.

[0077] The secondary muffler pipe 215 has a secondary pipe wall 229, which is tubular and includes a second set of perforations 231. The secondary pipe wall 229 extends linearly between the upstream secondary pipe end 233 and the downstream secondary pipe end 235 (i.e., the secondary muffler pipe 215 is a straight pipe or pipe). The secondary inlet header 206b includes a secondary inlet orifice 237, which receives the upstream secondary pipe end 233 with a close tolerance fit. The downstream end of the secondary inlet pipe 205 is received in the secondary inlet orifice 237 and the upstream secondary pipe end 233 with a close tolerance fit to form an overlapping joint. The secondary outlet header 208b includes a secondary outlet orifice 225b, which receives the downstream secondary pipe end 235 with a close tolerance fit. The upstream end of the secondary outlet pipe 207b is received in the secondary outlet orifice 225b and the downstream secondary pipe end 235 with a close tolerance fit to form an overlapping joint. Thus, the secondary muffler conduit 215 is arranged in fluid communication with the secondary inlet pipe 205 and the secondary outlet pipe 207 b and carries exhaust gas therebetween to define a secondary exhaust gas flow path 238 through the muffler 201 .

[0078] A first set of perforations 218 in the primary duct wall 217 is arranged in fluid communication with the primary resonator chamber 251 and is designed to propagate sound from the primary muffler duct 213 into the primary resonator chamber 251. A second set of perforations 231 in the secondary duct wall 229 is arranged in fluid communication with the secondary resonator chamber 253 and is designed to propagate sound from the secondary muffler duct 215 into the secondary resonator chamber 253. The primary resonator chamber 251 and / or the secondary resonator chamber 253 may contain a sound damping material 255, such as fiberglass roving.

[0079] The main resonator 239 has a main resonator cross-sectional area A1 defined by the housing 204a of the main resonator housing 202a, and the main muffler pipe 213 has a main muffler pipe cross-sectional area a1 that is smaller than the main resonator cross-sectional area A1. The sub-resonator 241 has a sub-resonator cross-sectional area A2 defined by the housing 204b of the sub-resonator housing 202b, and the sub-muffler pipe 215 has a sub-muffler pipe cross-sectional area a2 that is smaller than the sub-resonator cross-sectional area A2. It should be understood that the main resonator cross-sectional area A1 and the main muffler pipe cross-sectional area a1 are substantially perpendicular to the exhaust flow passing through / along the main exhaust flow path 227, and the sub-resonator cross-sectional area A2 and the sub-muffler pipe cross-sectional area a2 are substantially perpendicular to the exhaust flow passing through / along the sub-exhaust flow path 238. The sizes of the main resonator 239 and the sub-resonator 241 and the main muffler pipe 213 and the sub-muffler pipe 215 are set so that the main area ratio A1 / a1 of the main resonator cross-sectional area A1 divided by the main muffler pipe cross-sectional area a1 is less than the sub-area ratio A2 / a2 of the sub-resonator cross-sectional area A2 divided by the sub-muffler pipe cross-sectional area a2. For example, the sizes of the main resonator 239 and the main muffler pipe 213 are set so that the main area ratio A1 / a1 of the main resonator cross-sectional area A1 divided by the main muffler pipe cross-sectional area a1 may be greater than 1 and less than 4. The sizes of the sub-resonator 241 and the sub-muffler pipe 215 are set so that the sub-area ratio A2 / a2 of the sub-resonator cross-sectional area A2 divided by the sub-muffler pipe cross-sectional area a2 may be greater than 4 and less than 100. This particular geometry enables the second (quieter) operating mode of the muffler 201 to reduce the sound level produced by the vehicle exhaust system 10 at any given engine speed (rpm) without significantly affecting the exhaust note (i.e., frequency, pitch, resonance, burrs, etc.). Thus, the acoustic characteristics of the exhaust note remain the same in the first operating mode and the second operating mode, the exhaust sound is simply quieter (i.e., at a lower decibel level) in the second operating mode.

[0080] Another alternative is Fig. 7A ' and identified at reference numeral 201'. Muffler 201' is substantially similar to muffler 201. Therefore, similar elements will be identified with the same reference numerals including an apostrophe suffix. Muffler 201' differs from muffler 201 primarily in that a connector 210' is provided to allow fluid communication between the main resonator chamber 251' and the secondary resonator chamber 253'. It is contemplated that connector 210' is a hollow tube extending through each of housing 204a' and housing 204b'. Additional connectors 210' may also optionally be provided to fluidically interconnect the main resonator chamber 251' with the secondary resonator chamber 253'.

[0081] Figure 7B Another alternative muffler is depicted, identified by reference numeral 201". Muffler 201" is substantially similar to muffler 201, such that similar elements will be identified with the same numerals including a double prime suffix. The primary difference between muffler 201 and muffler 201" is the removal of the Figure 7 The second joint 209b is shown. In the alternative muffler 201", the secondary outlet pipe 207b" does not turn toward the main outlet pipe 207a", but continues to extend straight and remains spaced apart from the main outlet pipe 207a". The distal end 212a" of the main outlet pipe 207a" defines the main outlet pipe orifice 214a". The distal end 212b" of the secondary outlet pipe 207b" defines the secondary outlet pipe orifice 214b". Figure 4B In a manner similar to the muffler 101b shown in FIG. 1 , the exhaust flow path 227 ″ and the exhaust flow path 238 ″ remain separate from one another, with no physical interconnection between the exhaust flow paths downstream of the decay volume.

[0082] In view of the above teachings, many modifications and variations of the present application are possible and can be implemented in a manner different from that specifically described within the scope of the appended claims. These previous discussions should be interpreted as covering any combination of novel practices and their practicality of the present application. With respect to the methods described in the present application, the order of the steps may be separated from the order in which they appear without departing from the scope of the present application and the appended method claims. In addition, the various steps of the method may be performed in sequence or simultaneously.

Claims

1. A muffler assembly for a vehicle exhaust system, comprising: a muffler comprising a main resonator having a main resonator chamber and a sub-resonator having a sub-resonator chamber; a main muffler conduit passing through the main resonator chamber to define a main exhaust flow path through the muffler; a secondary muffler conduit extending through at least a portion of the secondary resonator chamber to define a secondary exhaust flow path within the muffler; and a valve positioned upstream of the primary resonator, the valve being actuatable between an open position and a closed position, wherein when the valve is in the open position, exhaust gas flow is permitted through both the primary muffler conduit and the primary exhaust flow path and through the secondary muffler conduit and the secondary exhaust flow path to produce a first level of sound attenuation provided by the muffler in a first operating mode, wherein the valve restricts exhaust flow through the primary muffler conduit and the primary exhaust flow path in the closed position such that when the valve is in the closed position, more than 50% of the exhaust flow is directed through the secondary muffler conduit and the secondary exhaust flow path to produce a second level of sound attenuation provided by the muffler in a second operating mode, the second level of sound attenuation being greater than the first level of sound attenuation provided by the muffler in the first operating mode, wherein the main resonator has a main resonator cross-sectional area (A1), and the main muffler pipe has a main muffler pipe cross-sectional area (a1) smaller than the main resonator cross-sectional area (A1), wherein the sub-resonator has a sub-resonator cross-sectional area (A2), and the sub-muffler pipe has a sub-muffler pipe cross-sectional area (a2) smaller than the sub-resonator cross-sectional area (A2), The sizes of the main resonator and the sub-resonator as well as the main muffler pipe and the sub-muffler pipe are set so that a main area ratio (A1 / a1) of the main resonator cross-sectional area (A1) divided by the main muffler pipe cross-sectional area (a1) is smaller than a secondary area ratio (A2 / a2) of the sub-resonator cross-sectional area (A2) divided by the sub-muffler pipe cross-sectional area (a2).

2. The muffler assembly according to claim 1, further comprising: a main inlet pipe arranged in fluid communication with the main muffler conduit; and A secondary inlet pipe is arranged in fluid communication with the secondary muffler conduit and is connected to the primary inlet pipe at a first junction outside the muffler. 3 . The muffler assembly of claim 2 , wherein the main resonator comprises a main resonator housing, and the sub-resonator comprises a sub-resonator housing separate and spaced apart from the main resonator housing.

4. The muffler assembly according to claim 3, further comprising: a main outlet pipe arranged in fluid communication with the main muffler conduit; and A secondary outlet pipe is arranged in fluid communication with the secondary muffler conduit and is connected to the primary outlet pipe at a second junction outside the muffler.

5. The muffler assembly of claim 4 , wherein the main muffler pipe has a perforated main pipe wall, the main pipe wall being tubular in shape and extending linearly from the main inlet pipe through the main resonator housing to the main outlet pipe, and wherein the secondary muffler pipe has a perforated secondary pipe wall, the secondary pipe wall being tubular in shape and extending linearly from the secondary inlet pipe through the secondary resonator housing to the secondary outlet pipe.

6. The muffler assembly of claim 3, further comprising: a main outlet pipe disposed in fluid communication with the main muffler conduit and comprising a main outlet pipe orifice; and A secondary outlet pipe is arranged in fluid communication with the secondary muffler conduit and includes a secondary outlet pipe orifice spaced apart from the primary outlet pipe orifice.

7. The muffler assembly of claim 6, further comprising: A single outlet pipe is disposed in fluid communication with the main muffler conduit.

8. The muffler assembly according to claim 4, wherein the main muffler pipe has a perforated main pipe wall, the main pipe wall is tubular in shape and extends linearly from the main inlet pipe through the main resonator shell to the single outlet pipe, wherein the main resonator is formed by a contraction tube, the contraction tube is positioned inside the muffler shell and above the main pipe wall, so that the main resonator chamber is formed between the main pipe wall and the contraction tube, wherein the secondary muffler pipe has a perforated secondary pipe wall, the secondary pipe wall is tubular in shape and extends within the muffler shell from the secondary inlet pipe to a second joint located inside the muffler shell, at the second joint, the secondary muffler pipe is joined to the main muffler pipe, and wherein the secondary resonator chamber is formed between the contraction tube and the muffler shell.

9. The muffler assembly of claim 1, wherein the muffler includes a connector fluidly connecting the primary resonator chamber to the secondary resonator chamber.

10. The muffler assembly of claim 3, wherein the valve is an active electromechanical valve including an electronic actuator connected to a movable valve member and driving movement of the movable valve member between the open position and the closed position.

11. The muffler assembly of claim 1 , wherein the primary muffler conduit and the secondary muffler conduit are perforated pipes, and wherein at least one of the primary resonator chamber and the secondary resonator chamber contains a sound dampening material.

12. The muffler assembly according to claim 1, wherein the main resonator cross-sectional area (A1) and the main muffler pipe cross-sectional area (a1) are substantially perpendicular to the exhaust flow passing through the main exhaust flow path, and wherein the sub-resonator cross-sectional area (A2) and the sub-muffler pipe cross-sectional area (a2) are substantially perpendicular to the exhaust flow passing through the sub-exhaust flow path.

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